The kinetics of demineralization of enamel and dentin surfaces will be studied at constant undersaturation, maintained by the glass electrode-controlled addition of acidified medium electrolyte. Surface erosion will range from softenting to the formation of subsurface lesions and the effectiveness of additives such as phosphonates and polyacrylates over a range of molecular weight in producing the lesions will be investigated by X-ray microradiography, microhardness tests, polarized light microscopy, EDAX, ESCA, and SIMS. The remineralization of these surfaces will be studied both in the presence and absence of carbon dioxide of known partial pressure at constant supersaturations. Concentrations in the mineralizing solutions will be controlled using both calcium and hdrogen ion electrodes. Transformation of acidic calcium phosphate phases to HAP wil be investigated at constant calcium phosphate concentration in the presence of both simple ions such as zinc, magnesium, copper, cadmium, aluminum, iron, fluoride and carbonate, as well as synthetic peptides and salivary proteins. The effectiveness of immobilized films of polypeptides and proteins in inducing the nucleation and growth of calcium phosphate phases will also be studied in an attempt to identify the factors important in the formation of hard ceramic-like calculus deposits in the biological milieu. The influence, upon both de- and re- mineralization, of cariogenic and cariostatic agents such as magnesium, strontium, fluoride, and carbonate will be investigated over a range of concentrations. Electrophoretic mobilities of enamel, dentin, calculus, and synthetic calcium phosphates will be determined in the presence of both simple inorganic ions and salivary proteins. Calculated surface potentials will be of considerable interest from the point of view of plaque adhesion.